Use of Linear Regression for the Processing of Curves of Differential Potentiometric Titration of a Binary Mixture of Heterovalent Ions Using Precipitation Reactions

A method is proposed for the computer processing of curves of differential potentiometric titration of a binary mixture of heterovalent ions using precipitation reactions. The method is based on the transformation of the titration curve to piecewise linear characteristics, whose parameters (within the accuracy of the least-squares method) determine the sequence of the equivalence points and solubility products of the resulting precipitates. The computational algorithm is implemented as a Turbo-Pascal program DIFTITR. The method is applied to the titration of Ag(I)-Cd(II), Hg(II)-Te(IV), and Cd(II)-Te(IV) mixtures by a sodium diethyldithiocarbamate solution with membrane sulfide and glassy carbon indicator electrodes. For 4 to 11 mg of the analyte in 50 mL of the solution, RSD varies from 1 to 9%.